This invention relates to a method and apparatus for improving elevator safety and more particularly for detecting intrusion into an elevator hoistway.
Persons that enter a hoistway, such as mechanics, maintenance personnel, and unauthorized persons may be injured by sudden unexpected movement of the elevator car. The condition of hoistway doors and elevator doors are constantly monitored to ensure that authorized personnel follow safety procedures when entering the hoistway and that no car movement is allowed upon entry of unauthorized personnel.
It is known in the prior art to monitor the switches on each landing door and the car door to determine if the doors are closed. The door switches from each door are normally wired in series to form a safety chain. High speed movement of the car is prevented whenever one of the doors is open. The car is allowed to resume normal operation when the doors are closed and the safety chain is made.
However, there exists a problem in the prior art in that if the elevator door and the corresponding landing door are open to allow passengers to enter or exit the car the safety chain is broken. A second open landing door cannot be detected. Therefore someone could enter the pit area at the bottom of the hoistway or step onto the top of the car from a landing above while the car is stopped for normal operation. Once all the doors are closed the elevator will resume normal operation which could result in injury to person above the car or in the pit.
Therefore there exists a need for an improved method and apparatus for detecting the presence of an unauthorized person entering the hoistway.
Objects of the invention include an improved method and apparatus for detecting the presence of an unauthorized person in the hoistway.
According to the present invention, a first safety chain is formed from the door sensors from the landings of the even numbered floors. A second safety chain is formed from the door sensors from the odd numbered floors and a third safety chain is formed from the door sensor from the pit door, which provides access to the pit at the bottom of the hoistway. In some elevator installations the bottom landing door also provides access to the pit.
The first, second, and third safety chains are monitored by software or logic located in the elevator controller. Depending on the status of the elevator car and safety chains the controller will allow the car to operate normally or stop the car and direct it to a nearest floor. The car will remain there until the controller receives a reset signal.
If no landing doors are open then there can be no entry to the hoistway. Therefore the controller will continue to monitor the status of three safety chains and allow normal operation.
In a first scenario, the controller will determine if the car is moving in normal operation and a landing door is open. If both conditions are satisfied, the controller will stop the car. The logic will then proceed to determine if either the pit door or another landing door above the car top is open. If either condition is satisfied the car will stop and after the door is closed, proceed to a landing, at low speed, and stop to allow passengers to exit. The car will remain there until a reset signal is received and the open pit and/or landing doors are closed. The car will then resume normal operation.
In a second scenario with the car stopped at a landing and the corresponding landing door open, the car will remain stopped upon detection of either an open pit door or an open door above the car. The elevator will be allowed to return to normal operation upon detection of a reset signal.